JP6308189B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system.

  The fuel cell system includes a cooling mechanism that cools the fuel cell so that the temperature of the fuel cell does not exceed a predetermined temperature during power generation. As this cooling mechanism, a liquid cooling type is known in which a fuel cell is cooled by circulating a coolant such as cooling water.

  Patent Document 1 discloses a liquid-cooled fuel cell system in which a cooling water passage through which cooling water for cooling the fuel cell circulates, a water pump for pumping the cooling water, and the temperature of the cooling water passing therethrough are lowered. A fuel cell system comprising a radiator is described.

JP 2010-267471 A JP 2007-311058 A

  In the fuel cell system described in Patent Document 1, when a high-load operation is temporarily performed, the amount of heat generated by the fuel cell may increase and the cooling water may temporarily become high temperature. As countermeasures against temporarily high temperatures of the cooling water, it is conceivable to increase the performance of the radiator and ensure the heat dissipation of the cooling water. However, if such countermeasures are taken, the problem is that the radiator becomes large. There is.

  The present invention has been made in view of the above background, and an object of the present invention is to provide a fuel cell system capable of suppressing the temperature of the cooling water from temporarily becoming high without increasing the size of the radiator. .

  The present invention is a fuel cell system, comprising a fuel cell, a radiator for lowering a temperature of a refrigerant that cools the fuel cell, a first flow path through which the refrigerant flows from the fuel cell toward the radiator, and a refrigerant A second flow path that flows from the radiator toward the fuel cell; an inflow refrigerant temperature detection unit that detects a refrigerant temperature flowing into the fuel cell in the second flow path; a position downstream of the radiator; A bypass channel connecting the upstream side of the inflow refrigerant temperature detection unit in the two channels, an open / close valve for switching between opening and blocking of the bypass channel, and storing the refrigerant provided in the bypass channel A reserve tank that controls the operation of the on-off valve using the refrigerant temperature detected by the inflow refrigerant temperature detection unit. When the refrigerant temperature detected by the medium temperature detection unit exceeds a predetermined reference temperature, the open / close valve is opened, and the refrigerant in the reserve tank is supplied from the radiator and flows through the second flow path. The refrigerants stored in advance are combined and supplied to the fuel cell. Thereby, it can suppress that cooling water becomes high temperature temporarily, without enlarging a radiator.

  And an outflow refrigerant temperature detector for detecting a refrigerant temperature immediately after flowing out of the fuel cell in the first flow path, a position upstream of the radiator in the first flow path, the reserve tank, and the second A second bypass flow channel connecting the flow channel, and a connecting portion between the first flow channel and the second bypass flow channel, and the amount of refrigerant flowing from the first flow channel into the radiator and the first flow channel A three-way valve that adjusts the amount of refrigerant flowing from one flow path into the second bypass flow path, wherein the control section is a second refrigerant temperature that is detected in advance by the refrigerant temperature detected by the outflow refrigerant temperature detection section. When the temperature is equal to or lower than the reference temperature, the opening degree of the three-way valve is adjusted so that all the refrigerant flows from the first flow path into the second bypass flow path. Thereby, a low temperature refrigerant | coolant can be stored in a reserve tank.

  Further, the control unit is configured so that, when the refrigerant temperature detected by the outflow refrigerant temperature detection unit exceeds a predetermined second reference temperature, all the refrigerant flows into the radiator from the first flow path. While adjusting the opening degree of a three-way valve, the said on-off valve is closed. Thereby, the refrigerant accumulated in the reserve tank can be maintained at a low temperature.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that a cooling water becomes high temperature temporarily, without enlarging a radiator.

It is a figure which shows schematic structure of the fuel cell system concerning this Embodiment. In the fuel cell system concerning this Embodiment, it is a figure which shows the state which opened the on-off valve. 4 is a flowchart showing a flow of a process for controlling a refrigerant supply operation from a reserve tank 35 based on a refrigerant temperature detected by an inflow refrigerant temperature detector in the fuel cell system according to the present embodiment. It is a figure explaining an example of the method of storing a low-temperature refrigerant | coolant in a reserve tank in the fuel cell system concerning this Embodiment. It is a figure explaining an example of the method of storing a low-temperature refrigerant | coolant in a reserve tank in the fuel cell system concerning this Embodiment. 4 is a flowchart showing a flow of processing for storing a low-temperature refrigerant in a reserve tank in the fuel cell system according to the present embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of a fuel cell system according to the present invention. The fuel cell system 1 includes a fuel cell stack 2 as a fuel cell, a cooling mechanism 3 that cools the fuel cell stack 2, and a control unit 4.

  The fuel cell stack 2 is configured by stacking a plurality of fuel cell cells formed by sandwiching an electrolyte membrane such as a solid polymer ion exchange membrane from both sides by an anode electrode (fuel electrode) and a cathode electrode (oxidant electrode). Is done. When a fuel cell supplies an anode gas containing hydrogen to an anode electrode and supplies air containing oxygen to a cathode electrode, hydrogen ions generated at the anode electrode by a catalytic reaction pass through an electrolyte membrane to the cathode electrode. It moves and generates electricity by causing a chemical reaction between hydrogen ions and oxygen at the cathode electrode. Water is generated when a chemical reaction between hydrogen ions and oxygen occurs at the cathode electrode. The fuel cell stack 2 is configured by stacking several hundred fuel cells to obtain a large amount of power necessary for driving a vehicle such as an automobile.

  The cooling mechanism 3 includes a radiator 30, a first flow path 31, a second flow path 32, an inflow refrigerant temperature detection unit 33, a bypass flow path 34, a reserve tank 35, and an opening / closing valve 36. Yes. The radiator 30 reduces the temperature of a coolant such as cooling water that cools the fuel cell stack 2. The first flow path 31 is a flow path in which the refrigerant flows from the fuel cell stack 2 toward the radiator 30. The second flow path 32 is a flow path in which the refrigerant flows from the radiator 30 toward the fuel cell stack 2. The inflow refrigerant temperature detection unit 33 is a temperature sensor and detects the refrigerant temperature just before flowing into the fuel cell stack 2 in the second flow path 32. The bypass flow path 34 connects the radiator 30 (the refrigerant outlet of the radiator 30) and a position upstream of the inflow refrigerant temperature detection unit 33 in the second flow path 32. The bypass passage 34 is provided with a reserve tank 35 for storing refrigerant and an opening / closing valve 36. The reserve tank 35 is provided at a position downstream of the opening / closing valve 36 in the bypass flow path 34. The on-off valve 36 switches between opening and shutting off the bypass channel 34.

  The cooling mechanism 3 further includes an outflow refrigerant temperature detection unit 37, a second bypass flow path 38, a three-way valve 39, and a water pump 40. The outflow refrigerant temperature detection unit 37 detects the refrigerant temperature immediately after flowing out of the fuel cell stack 2 in the first flow path 31. The second bypass flow path 38 connects the position on the upstream side of the radiator 30 in the first flow path 31 to the reserve tank 35 and the second flow path 32. The three-way valve 39 is provided at a connection portion between the first flow path 31 and the second bypass flow path 38, and the amount of refrigerant flowing into the radiator 30 from the first flow path 31 and the second bypass flow from the first flow path 31. The amount of refrigerant flowing into the passage 38 is adjusted. Note that the three-way valve 39 may be an ON / OFF operation or an opening degree that changes stepwise (linearly).

  The water pump 40 is provided near the inlet of the fuel cell stack 2 in the second flow path 32, and causes the cooling mechanism 3 to circulate the refrigerant. In the water pump 40, the discharge flow rate continuously changes depending on the rotation speed.

  The control unit 4 includes a microcomputer including a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), an input / output interface (I / O interface), and the like. The control unit 4 controls the opening / closing of the opening / closing valve 36 based on the refrigerant temperature detected by the outflow refrigerant temperature detection unit 37. Further, the control unit 4 adjusts the opening degree of the three-way valve 39.

Next, processing for controlling the refrigerant supply operation from the reserve tank 35 based on the refrigerant temperature detected by the inflow refrigerant temperature detection unit 33 will be described below.
In order to sufficiently cool the fuel cell stack 2, it is necessary to maintain the refrigerant temperature immediately before flowing into the fuel cell stack 2 at a predetermined temperature or lower. When the refrigerant temperature immediately before flowing into the fuel cell stack 2 becomes equal to or higher than the output limit temperature (about 85 ° C.), the output of the fuel cell stack 2 is limited in order to prevent the temperature of the fuel cell stack 2 from rising excessively.

  In the present embodiment, when the refrigerant temperature immediately before flowing into the fuel cell stack 2 (the refrigerant temperature detected by the inflow refrigerant temperature detection unit 33) exceeds a predetermined reference temperature TB, the control unit 4 opens and closes. The valve 36 is opened, and the refrigerant previously stored in the reserve tank 35 is merged with the refrigerant supplied from the radiator 30 and flowing through the second flow path 32, and is supplied to the fuel cell stack 2. The reference temperature TB is set to a value lower than the output limit temperature. The temperature of the refrigerant in the reserve tank 35 is, for example, −35 to 57 ° C. Thereby, it is possible to maintain the refrigerant temperature immediately before flowing into the fuel cell stack 2 so as not to exceed the output limit temperature.

  FIG. 2 is a view showing a state in which the opening / closing valve 36 is opened. The opening degree of the three-way valve 39 is adjusted so that all the refrigerant flows from the first flow path 31 into the radiator 30. When the opening / closing valve 36 is opened, as shown in FIG. 2, the low-temperature refrigerant stored in advance in the reserve tank 35 and the refrigerant after radiating heat through the radiator 30 are connected to the bypass passage 34 and the second passage 32. At the connection part P1. Thereby, it can suppress that cooling water becomes high temperature temporarily, without enlarging a radiator.

  In the fuel cell system described in Patent Document 2, a flow path through which cooling water flows through a heat retaining tank that stores low-temperature cooling water, and a flow path through which cooling water flows without passing through the heat retaining tank (via a radiator). A normal flow path through which cooling water flows) and two flow paths (closed circuit) that can be switched between, and when the temperature of the fuel cell exceeds a predetermined temperature, the normal flow of cooling water through the radiator The flow path is switched from the flow path to the flow path through which the cooling water flows through the heat retaining tank. However, in the fuel cell system described in Patent Document 2, only one of the flow path through which the cooling water flows through the heat retaining tank and the normal flow path through which the cooling water flows through the radiator circulates the cooling water. .

  On the other hand, in the present invention, the refrigerant temperature just before flowing into the fuel cell stack 2 is obtained by joining the refrigerant after radiating heat through the radiator 30 with the low-temperature refrigerant stored in the reserve tank 35 in advance. Can be quickly suppressed below the output limit temperature. As a result, the fuel cell can be more sufficiently cooled when the operating load of the fuel cell system rises temporarily.

  In addition, the control for supplying the refrigerant stored in the reserve tank 35 in advance to the refrigerant flowing through the second flow path 32 is performed by controlling the temperature of the cooling water immediately after flowing out of the fuel cell stack 2 or the inside of the fuel cell stack 2. Although it is conceivable to perform the measurement based on the directly measured temperature, if the control is performed based on the refrigerant temperature immediately before flowing into the fuel cell stack 2 (the refrigerant temperature detected by the inflow refrigerant temperature detection unit 33), the control is performed with better response. be able to. For this reason, it is possible to quickly cope with a sudden increase in the operating load of the fuel cell system 1.

  In the fuel cell system 1, the time that can cope with a temporary increase in operating load depends on the capacity of the reserve tank 35. For example, on a highway 73 in the United States where the undulations are particularly high, driving a route with a maximum slope of 6.3% at a vehicle speed of 75 miles / hour takes about 65 seconds to pass this route. It is considered that high-load operation continues in the fuel cell system 1 while the vehicle passes through such a steep route. Therefore, in the design of the fuel cell system 1, the capacity of the reserve tank 35 may be determined according to the length of time that the high load operation is assumed to continue.

  FIG. 3 is a flowchart showing a flow of processing for switching opening / closing of the opening / closing valve 36 according to the refrigerant temperature detected by the inflow refrigerant temperature detection unit 33. In the following description, reference will also be made to FIG. 1 as appropriate. As shown in FIG. 3, first, it is determined whether or not the refrigerant temperature (T2) detected by the inflow refrigerant temperature detection unit 33 exceeds a predetermined reference temperature TB (step S1). When it is determined that the refrigerant temperature (T2) detected by the inflow refrigerant temperature detection unit 33 in step S1 exceeds a predetermined reference temperature TB (T2> TB) (YES in step S1), the opening / closing valve 36 is opened. Alternatively, it is maintained in the opened state (step S2). When it is determined that the refrigerant temperature (T2) detected by the inflow refrigerant temperature detection unit 33 in step S1 does not exceed a predetermined reference temperature TB (T2 ≦ TB) (NO in step S1), the open / close valve 36 is closed or kept in a closed state (step S3). During the operation of the fuel cell system 1, the processes of steps S1 to S3 are repeated.

  By switching the opening / closing of the opening / closing valve 36 as described above, it is possible to prevent the temperature of the refrigerant circulating in the cooling mechanism from exceeding the limit temperature due to a temporary increase in operating load.

Next, a method for storing the low-temperature refrigerant in the reserve tank 35 will be described below.
4 and 5 are diagrams illustrating an example of a method for storing a low-temperature refrigerant in the reserve tank 35. FIG. When the refrigerant temperature (T1) detected by the outflow refrigerant temperature detector 37 is equal to or lower than a predetermined second reference temperature TB2 (operation target temperature: about 57 ° C.) (T1 ≦ TB2), as shown in FIG. The control unit 4 adjusts the opening degree of the three-way valve 39 so that all the refrigerant flows from the first flow path 31 into the second bypass flow path 38 and opens the open / close valve 36. As described above, the second bypass flow path 38 connects the position on the upstream side of the radiator 30 in the first flow path 31 to the reserve tank 35 and the second flow path 32. That is, when the refrigerant temperature (T1) detected by the outflow refrigerant temperature detection unit 37 is equal to or lower than the second reference temperature TB2 (T1 ≦ TB2), it is determined that the temperature of the refrigerant circulating in the cooling mechanism 3 is low. The refrigerant is not allowed to flow from the first flow path 31 to the radiator 30 but is flowed from the first flow path 31 to the reserve tank 35 and the second flow path 32, and the low-temperature refrigerant is stored in the reserve tank 35. In the reserve tank 35, a low-temperature refrigerant of about −30 to 57 ° C. is stored. The second bypass flow path 38 may connect the reserve tank 35 with a position upstream of the radiator 30 in the first flow path 31. In this way, all the refrigerant flows into the reserve tank 35 from the first flow path 31 through the second bypass flow path 38.

  On the other hand, when the refrigerant temperature (T1) detected by the outflow refrigerant temperature detection unit 37 exceeds a predetermined second reference temperature TB2 (T1> TB2), as shown in FIG. The opening degree of the three-way valve 39 is adjusted so that the refrigerant flows into the radiator 30 from the first flow path 31, and the open / close valve 36 is closed. That is, when the refrigerant temperature (T1) detected by the outflow refrigerant temperature detection unit 37 exceeds the second reference temperature TB2 (T1> TB2), it is determined that the temperature of the refrigerant circulating in the cooling mechanism 3 is relatively high, This relatively high temperature refrigerant is prevented from flowing into the reserve tank 35. Thereby, the refrigerant | coolant collected in the reserve tank 35 can be maintained at low temperature.

  FIG. 6 is a flowchart showing a process flow for storing the low-temperature refrigerant in the reserve tank 35. In the following description, reference will also be made to FIG. 1 as appropriate. As shown in FIG. 6, first, it is determined whether or not the refrigerant temperature (T1) detected by the outflow refrigerant temperature detection unit 37 is equal to or lower than a predetermined second reference temperature (operation target temperature) TB2 (step S101). ). When it is determined that the refrigerant temperature (T1) detected by the outflow refrigerant temperature detection unit 37 in step S101 is equal to or lower than a predetermined second reference temperature TB2 (T1 ≦ TB2) (in the case of YES in step S101), all The degree of opening of the three-way valve 39 is adjusted so that the refrigerant flows from the first flow path 31 into the second bypass flow path 38, and the open / close valve 36 is opened (step S102).

  When it is determined in step S101 that the refrigerant temperature (T1) detected by the outflow refrigerant temperature detection unit 37 exceeds a predetermined second reference temperature TB2 (T1> TB2) (NO in step S101) The opening degree of the three-way valve 39 is adjusted so that all the refrigerant flows into the radiator 30 from the first flow path 31, and the open / close valve 36 is closed (step S103). During the operation of the fuel cell system 1, the processes of steps S101 to S103 are repeated.

  In the process flow of FIG. 3, when it is determined that the refrigerant temperature (T2) detected by the inflow refrigerant temperature detector 33 in step S1 does not exceed a predetermined reference temperature TB, the open / close valve is determined in step S3. 36 was closed. On the other hand, when performing the process which stores a low-temperature refrigerant | coolant in the reserve tank 35 with the flow demonstrated using FIG. 6, the process of FIG.6 S102 is prioritized with respect to the process of FIG.3 S3. That is, it is determined that the refrigerant temperature (T2) detected by the inflow refrigerant temperature detection unit 33 does not exceed a predetermined reference temperature TB, and the refrigerant temperature (T1) detected by the outflow refrigerant temperature detection unit 37 is When it is determined that the temperature is equal to or lower than the predetermined second reference temperature TB2, the opening degree of the three-way valve 39 is adjusted so that all the refrigerant flows from the first flow path 31 into the second bypass flow path 38, and is opened and closed. Open the valve 36.

  As described above, low-temperature refrigerant can be stored in the reserve tank 35 by adjusting the opening of the three-way valve and the opening / closing of the opening / closing valve 36.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention.

  For example, the method for storing the low-temperature refrigerant in the reserve tank is not limited to the method described in the above embodiment.

  The opening / closing valve 36 may be opened / closed based on position information of a navigation system installed in the vehicle. That is, the navigation system may obtain information on the road to be passed (for example, the slope is steep), and open / close the valve 36 by predicting a high load operation from the information.

DESCRIPTION OF SYMBOLS 1 Fuel cell system 2 Fuel cell stack 3 Cooling mechanism 4 Control part 30 Radiator 31 1st flow path 32 2nd flow path 33 Inflow refrigerant | coolant temperature detection part 35 Reserve tank

Claims (2)

A fuel cell;
A radiator for lowering a temperature of a refrigerant for cooling the fuel cell;
A first flow path through which a refrigerant flows from the fuel cell toward the radiator;
A second flow path through which the refrigerant flows from the radiator toward the fuel cell;
An inflow refrigerant temperature detector for detecting a refrigerant temperature flowing into the fuel cell in the second flow path;
A bypass flow path that connects a position on the downstream side of the radiator and a position on the upstream side of the inflow refrigerant temperature detection unit in the second flow path;
An open / close valve that switches between opening and closing the bypass flow path;
A reserve tank that is provided in the bypass passage and stores the refrigerant;
A controller that controls the operation of the open / close valve using the refrigerant temperature detected by the inflow refrigerant temperature detector;
The control unit opens the on-off valve when the refrigerant temperature detected by the inflow refrigerant temperature detection unit exceeds a predetermined reference temperature, and is supplied from the radiator and flows through the second flow path In contrast, the refrigerant stored in the reserve tank in advance is merged and supplied to the fuel cell ,
An outflow refrigerant temperature detector for detecting the refrigerant temperature immediately after flowing out of the fuel cell in the first flow path;
A second bypass flow path that connects a position upstream of the radiator in the first flow path, the reserve tank, and the second flow path;
Provided at the connection between the first flow path and the second bypass flow path, the amount of refrigerant flowing from the first flow path into the radiator and from the first flow path to the second bypass flow path A three-way valve for adjusting the amount of refrigerant,
When the refrigerant temperature detected by the outflow refrigerant temperature detection unit is equal to or lower than a predetermined second reference temperature, all the refrigerant flows into the second bypass channel from the first channel. A fuel cell system that adjusts the opening of the three-way valve as described above . When the refrigerant temperature detected by the outflow refrigerant temperature detection unit exceeds a predetermined second reference temperature, the control unit controls the three-way valve so that all the refrigerant flows from the first flow path into the radiator. the fuel cell system according to claim 1 together with adjusting the opening, closing the opening and closing valve.

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